Use the new way to specify mingw32 for ffmpeg

extras/contrib/src/Makefile

@@ -115,7 +115,7 @@ endif
 #
 ifdef HAVE_WIN32
 HOSTCONF+= --without-pic --disable-shared --enable-msw --with-included-opencdk --with-included-libtasn1 --disable-dependency-tracking
-FFMPEGCONF+= --enable-mingw32 --enable-memalign-hack --cpu=x86 --disable-debug
+FFMPEGCONF+= --target-os=MINGW32 --enable-memalign-hack --cpu=i686 --disable-debug
 endif
 
 ifdef HAVE_WINCE